Re: [PATCH 1/1] generic: test FALLOC_FL_UNSHARE when pagecache is not loaded

["Darrick J. Wong" <djwong@kernel.org>]

On Tue, Sep 26, 2023 at 10:51:19AM +0530, Ritesh Harjani wrote:
> "Darrick J. Wong" <djwong@kernel.org> writes:
> 
> > From: Darrick J. Wong <djwong@kernel.org>
> >
> > Add a regression test for funsharing uncached files to ensure that we
> > actually manage the pagecache state correctly.
> >
> > Signed-off-by: Darrick J. Wong <djwong@kernel.org>
> > ---
> >  tests/xfs/1936     |   88 ++++++++++++++++++++++++++++++++++++++++++++++++++++
> >  tests/xfs/1936.out |    4 ++
> >  2 files changed, 92 insertions(+)
> >  create mode 100755 tests/xfs/1936
> >  create mode 100644 tests/xfs/1936.out
> >
> >
> > diff --git a/tests/xfs/1936 b/tests/xfs/1936
> > new file mode 100755
> > index 0000000000..e07b8f4796
> > --- /dev/null
> > +++ b/tests/xfs/1936
> > @@ -0,0 +1,88 @@
> > +#! /bin/bash
> > +# SPDX-License-Identifier: GPL-2.0
> > +# Copyright (c) 2023 Oracle.  All Rights Reserved.
> > +#
> > +# FS QA Test 1936
> > +#
> > +# This is a regression test for the kernel commit noted below.  The stale
> > +# memory exposure can be exploited by creating a file with shared blocks,
> > +# evicting the page cache for that file, and then funshareing at least one
> > +# memory page's worth of data.  iomap will mark the page uptodate and dirty
> > +# without ever reading the ondisk contents.
> > +#
> > +. ./common/preamble
> > +_begin_fstest auto quick unshare clone
> > +
> > +_cleanup()
> > +{
> > +	cd /
> > +	rm -r -f $tmp.* $testdir
> > +}
> > +
> > +# real QA test starts here
> > +
> > +# Import common functions.
> > +. ./common/filter
> > +. ./common/attr
> 
> We might as well remove above imports if we are not using those in this test.

<nod>

> > +. ./common/reflink
> > +
> > +_fixed_by_git_commit kernel XXXXXXXXXXXXX \
> > +	"iomap: don't skip reading in !uptodate folios when unsharing a range"
> 
> Once I guess it is merged, we will have the commit-id. Ohh wait, we have
> it already right? 
> 
> https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=35d30c9cf12730a1e37053dfde4007c7cc452d1a

Oops, yeah, I'll update the tag.

> With that the testcode looks good to me. Thanks for finding an easy
> reproducer. Please feel free to add - 
> 
> Reviewed-by: Ritesh Harjani (IBM) <ritesh.list@gmail.com>

Thanks!

> -ritesh